The invention relates to a driveshaft for use in a driveline to drive wheels of a motor vehicle. The driveshaft has two constant velocity joints each having a first joint part with connecting means to establish a connection with a driving or driven part of the driveline. Each joint has a second joint part. The two constant velocity joints are connected to one another by a connecting shaft. The two joints are designed as constant velocity fixed joints which enable only angular movements between their two respective joint parts. The driveshaft also includes means for enabling a change in the distance between the connecting means.
U.S. Pat. No. 4,950,206 issued Aug. 21, 1990, discloses a driveshaft wherein the second joint part of one of the constant velocity joints is extended in a sleeve-like way and includes a bore provided with running grooves. The connecting shaft is inserted into the bore and, on its outer face, it also includes running grooves arranged so as to correspond to those of the second joint part. The opposed running grooves contain rolling contact members in the form of balls. The axial movement of the connecting shaft relative to the second joint part is limited by stops. The connecting shaft is a solid shaft and designed to be integral with the second joint part of the other constant velocity joint. Furthermore, it is possible to assemble the connecting shaft from a thin-walled tube and two journals, with one of the journals directly connected to the second joint part of the other joint without the plunging facility.
In such an embodiment, the size of the constant velocity joint has to be such that it is adapted to the cross-section of the plunging part, which, with respect to diameter, is dimensioned to meet torque transmitting requirements. This means that the diameter of the joint has to be greater than that normally required for torque transmitting purposes. Furthermore, the second joint part, which constitutes the inner part, in addition to including space to accommodate the journal, is provided with a radial wall thickness between the bore and inner running track, which takes account the respective strength requirements.
DE 41 19 451 C2, issued Mar. 25, 1993, describes a jointed shaft intended to be used as a steering shaft for motor vehicles. It consists of the joints provided in the form of universal joints, and a plunging part. The plunging part includes a two-rib tube. The two ribs form running grooves. An inner part associated with two ball circulation guides offset by 180.degree. is inserted into the two-rib tube. Such a design is complicated and expensive and requires a great deal of space to accommodate the two ball circulation guides. With steering shafts, such space is available. Furthermore, in the case of steering shafts, the mass to be moved is of no great significance as the steering shaft is moved for the purpose of the steering movement only and the resulting speeds are extremely low.